Salinity and Bulk Water Workshop 27 October 2010 Werribee Irrigation District

Salinity and Bulk Water Workshop 27 October 2010

Werribee Irrigation District

Today’s workshop

1. Welcome and outline of workshop2. Bulk water discussion

a. Metro water overview – Ian Smith, Melbourne Waterb. Allocation models for river water

3. Soil monitoring resultsa. Update on 2010 soil testing results and analysis – Tony Pitt

Break4. Bulk supply management discussion

a. Managing access to river/recycled/metro water5. Close

Bulk water discussion

Melbourne Water

New River Allocation Model

Some context…

• 13 years of drought• Few years of good river water allocations (except 04/05; 05/06,

10/11)• Allocations less than 15% from 2006/07 until this year.• Historic allocation system:

1. Allocate available water for this year to 100%

2. Put aside 10,000ML for next season

3. Then allocate sales (Low Reliability Water Share)Current allocation system puts away water for next season before we reach 100%

How we propose to allocate available water between 50% – 100% of entitlement

Example 150% of entitlement available this year

Example 150% of entitlement available this yearplus further inflows to allow an extra 30% allocation

Example 150% of entitlement available this yearplus 30% further inflows – split 50:50 this year:next year

Example 1So allocation this year is 65% (50+15) plus 15%* towards next year

Example 265% of entitlement available this year plus greater inflows

Example 265% of entitlement available this yearplus further inflows to allow an extra 20% allocation

Example 265% of entitlement available this yearplus 20% further inflows – split 50:50 this year:next year

Example 2So allocation this year is 75% (65+10) plus 25%* towards next year

How we propose to allocate available water above 100% of entitlement

Example 1So if we have 75% of entitlement available this year (from previous example)

Example 175% of entitlement available this yearplus further inflows to allow an extra 25% allocation

Example 175% of entitlement available this yearplus further inflows to allow an extra 25% allocationyou keep 100% of entitlement

Example 2100% of entitlement available this yearplus 25% further inflows

Example 2 100% of entitlement available this yearplus 25% further inflows – split 50:50

Example 2 New allocation this year 100% plus 37.5%* towards next year and 12.5% Sales

Allocation scenario = 100% HRWS + 12.5% LRWS in 1st year 37.5% in 2nd year

0%

20%

40%

60%

80%

100%

120%

140%

160%

10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110% 120% 125% 130% 140% 150% 48%

Available water

All

oc

ati

on

minimal inflows

HRWS 2011/12

LRWS 2011/12

HRWS 2011/12

LRWS 2010/11

HRWS 2010/11

Benefits of the 2010/11 allocation method

• More conservative; recognises less reliable river flows• Provides more security for following seasons• Manages water to stretch further over dry seasons• Provides a more certain planning horizon for irrigators in dry times

Looking to the future:Continuous Sharing

Continuous sharing …

• Is a method of water accounting• Used in Victoria for large electricity customers in Gippsland• Used in areas of Queensland since 1999

• Growers interest is growing in other parts of Queensland

• Growers have increased production without increasing water use through better water management due to continuous sharing

Continuous sharing provides more individual choice and requires more decision making.However – customers can choose to take standard allocations if they want.

Example of continuous sharing…

Reservoir Inflows less storage losses and environmental flows

Outflows plus delivery losses

Your storage share…

Reservoir

Outflows plus delivery losses

Inflows less storage losses and environmental flows

Your storage share…

Reservoir

Outflows plus delivery losses

Inflows less storage losses and environmental flows

Your storage share…

Reservoir

Outflows plus delivery losses

Inflows less storage losses and environmental flows

Your storage share…

Reservoir

Outflows plus delivery losses

Inflows less storage losses and environmental flows

Your storage share…

Reservoir

Outflows plus delivery losses

Inflows less storage losses and environmental flows

Your storage share…

Reservoir

Outflows plus delivery losses

Inflows less storage losses and environmental flows

Your storage share…

Reservoir

Outflows plus delivery losses

Inflows less storage losses and environmental flows

Your storage share…

Reservoir

Outflows plus delivery losses

Inflows less storage losses and environmental flows

Your limit on seasonal use…

Total Annual Use Limit

Your seasonal cap…

Total Annual Entitlement

Your seasonal cap…

Total Annual Cap

You can trade seasonal cap

Continuous sharing example…Water share account

A

Storage 200ML

-10ML loss

=190ML

-65ML Rel

-10 ML loss

=115ML

-65ML Rel

-5ML loss

=45ML

+50ML trade

=95ML

+25ML inflow

=115ML

Entitlement Cap account

B

Storage 200ML

-10ML loss

=190ML

-0ML Rel

-15ML loss

=175 ML

-0ML Rel

-15 ML loss

=160 ML

-50ML traded

=110 ML

+25 ML Inflow

=140ML

A BEntitlement

100ML

0 ML use

=100 ML

-50 ML use

=50 ML

-50 ML use

=0 ML

+ 25 ML trade

=25 ML

Entitlement

100ML

0 ML use

=100ML

0 ML use

=100 ML

0 Ml use

=100 ML

-25 ML traded

=75 ML

A B

Next season115 ML 140 ML 100 ML 100 ML

What are the benefits of continuous sharing?

• You manage your water share at the storage• No annual allocation made for the district • There is no reset at the end of the season for water shares• The maximum you can store is limited by the size of your storage share• The maximum you can use in a season is capped• The maximum you can use is reset at the end of a season• You can separately trade: water, water share and entitlement caps• The legal water entitlement you currently hold remains the same• The maximum volume in your storage depends on your storage size • You share inflows based on your storage share • You share storage losses based on the volume you store• Your use includes delivery losses• The water you have depends on inflows, losses, use and trades • More flexibility can provide greater certainty and planning horizon

It’s like having your own storage

What next …

• Are you interested?• Customer support – If strong, proceed with initial study• Legislative changes are required – it will take time

• Develop model to suit local conditions • Develop information package for customers • Run information sessions and inform customers on continuous

allocation use

Soil management

Tony Pitt

Six years of soil testing

• In 2005/06, recycled water use was fairly minor – just 47 farms with more than 1 ML/ha.

• For 2006/07, recycled water underpinned crop production for Werribee

• For the following 4 years, recycled water was by far the dominant source of irrigation water for the district.

• The salinity of the recycled water is 1700 to 2300 EC– 1,700 uS/cm to 2,300 uS/cm – units used for irrigation water– 1.7 dS/m to 2.3 dS/m – units used for soil water.

Average Soil Salinity

0

1

2

3

4

5

6

7

8

Baseline 2006 2007 2008 2009 2010

ECe

dS/m

Soil Ece REIP Threshold

Average Soil Chloride

0

100

200

300

400

500

600

700

800

900

Baseline 2006 2007 2008 2009 2010

Conc

entr

ation

mg/

kg

Chloride REIP Threshold

Average Exchangeable Sodium Percentage (ESP)

0

2

4

6

8

10

12

14

16

18

20

Baseline 2006 2007 2008 2009 2010

ESP

%

ESP REIP Threshold Sodic

• Average surface soil salinity is back to baseline values

• District average chloride has fallen by 40 % in 12 months

• Sodium values however are unchanged• Sodicity is apparent when collecting soil samples

• Winter rainfall better but still below average

In 2010

• The Red Brown Earth soils of Werribee South are very forgiving and very responsive to rain

• The late summer and autumn period are the most important times for salinity management

• For every irrigated crop some leaching is required• A negative impact of rainfall on sodic soils is the

dispersion and sealing of the soil surface

Short term

• Natural leaching from rain will remove the surface salinity provided the soils are kept permeable

• Rain or low salinity water doesn’t improve sodicity• Sodicity requires continuous on-farm management• Gypsum dosing of the irrigation water could be better

option than broadcast gypsum

Long term

• Adding calcium– Gypsum broadcast– Gypsum added to water– Other calcium fertilizers

Sodicity management

In summary

• Werribee South soils can handle 2,000 to 2,200 EC water for a season or two with very good farm management

• Evidence from six years of soil testing indicates 1,300 EC –1,800 EC, with minimal leaching should be sustainable provided soil sodicity is kept under control

• Above 1,800 EC leaching has to increase and be planned for each crop

• Lower salinity water may increase the problems of surface sealing and poor aeration

• On-going sodicity management important

Break

Bulk supply management discussion

Planning Scenarios

River flow history

Lerderderg River seasonal inflow 1990/91 to 2009/10(Inflow at Sardine Creek site, Lerderderg ~ 40% of Werribee catchment flows)

-

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

55,000

60,000

65,000

70,000

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

06/0

7

07/0

8

08/0

9

09/1

0

10/1

1

Tota

l Sea

sona

l Flo

w (M

L/ye

ar)

Natural flow Average 20/21 to 89/90 Average 90/91 to 09/10

Average 97/98 to 09/10 Average 05/06 to 09/10 5 year rolling average

Worst caseMediumOptimistic

WIF Climate planning scenarios

Planning scenarios…

Planning scenarios…

Planning scenarios…

How do we use this information to revise the rules

River Water Salinity

Seasonal Allocation

Shandy Target

Less than Shandy Target

Between Shandy Target and 1,800EC

Greater than 1,800EC

Up to 50% 1,800EC Shandy

Target River Water Salinity

Salinity with maximum practical Recycled

Water

50% - 75% 1,600EC Shandy

Target River Water Salinity

Salinity with maximum practical Recycled

Water

75% - 100% 1,400EC Shandy

Target River Water Salinity

Salinity with maximum practical Recycled

Water

Above 100% 1,000EC Shandy

Target River Water Salinity

Salinity with maximum practical Recycled

Water

Possible Salinity Triggers

Adapting to a mixed water approach

Provides more security to customers– critical in low allocation years

Triggers for accessing metro water…

• Metro water is a back-up option only– When river and recycle water salinity too high– Becomes part of the shandy with river and recycled– Increases volume in dry years particularly in peak summer– Increases security of supply

• Considerations when very low river allocation– River water salinity likely to be higher than recycle water– Target salinity level for shandy– How the salinity target may change over the season– The benefit of extra volume in summer

• Planning scenarios

Wet year (100+% allocation) No metro water

Low allocation (50%+) Unlikely to use metro water

Very low allocation (<25%) Consider using metro water

$-

$500

$1,000

$1,500

$2,000

$2,500

$3,000

$3,500

1300 1550 1950 2200

Salinity (ECe)

Costs of Salinity Management Lettuce (per/ha/crop)

Metro WaterYield & Quality LossExtra Ca FertiliserGypsumExtra Water - Leaching

$-

$200

$400

$600

$800

$1,000

$1,200

$1,400

1300 1550 1950 2200

Salinity (ECe)

Cost of Salinity Management Broccoli (per/ha/crop)

Metro WaterExtra Ca FertiliserGypsumExtra Water - Leaching

Salinity targets…

• Summer threshold range from 1,500 – 1,800 EC– Depends on river allocation and salinity of river water

– Volume of metro water to be accessed

– Recycled salinity

– Soil health before summer

• Winter threshold range from 1,800 - 2,000 EC– Recycled water salinity lower in winter and <2,000 EC

– Crops can tolerate higher salinities in winter

• Salinity thresholds will require review by EPA

Shandy scenarios

0

500

1000

1500

2000

2500

500ML 1000ML 1500ML 2000ML

Metro water accessed

Sh

an

dy

EC

Jan Jan-Feb Dec-Feb Dec-March River/Recycle

Adapting to a Mixed Water Approach

Adapting to a mixed water approach

Provides more security to customers– critical in low allocation years

Adapting to a mixed water approach

Provides flexibility to adapt to different seasons

Adapting to a mixed water approach

River water will be the first choice– is unreliable– Salinity too high in low allocation seasons

Adapting to a mixed water approach

Recycled water very reliable– Limits on supply rate– Salinity 1700 – 2200 EC

Adapting to a mixed water approach

Metro water last choice– Very low salinity– Limits on daily volume– Can provide extra water at peak times

Close